Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933523AbbLORTL (ORCPT ); Tue, 15 Dec 2015 12:19:11 -0500 Received: from mail-ig0-f169.google.com ([209.85.213.169]:34368 "EHLO mail-ig0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933438AbbLORTI (ORCPT ); Tue, 15 Dec 2015 12:19:08 -0500 MIME-Version: 1.0 In-Reply-To: <566FE4E1.2040005@linux.intel.com> References: <20151215012955.GA28277@dtor-ws> <566FE4E1.2040005@linux.intel.com> Date: Tue, 15 Dec 2015 09:19:06 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] android: fix warning when releasing active sync point From: Dmitry Torokhov To: Maarten Lankhorst Cc: Dmitry Torokhov , Greg Kroah-Hartman , Sumit Semwal , =?UTF-8?B?QXJ2ZSBIasO4bm5ldsOl?= , Riley Andrews , Andrew Bresticker , linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, "linux-kernel@vger.kernel.org" , devel@driverdev.osuosl.org Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2433 Lines: 51 On Tue, Dec 15, 2015 at 2:01 AM, Maarten Lankhorst wrote: > Op 15-12-15 om 02:29 schreef Dmitry Torokhov: >> Userspace can close the sync device while there are still active fence >> points, in which case kernel produces the following warning: >> >> [ 43.853176] ------------[ cut here ]------------ >> [ 43.857834] WARNING: CPU: 0 PID: 892 at /mnt/host/source/src/third_party/kernel/v3.18/drivers/staging/android/sync.c:439 android_fence_release+0x88/0x104() >> [ 43.871741] CPU: 0 PID: 892 Comm: Binder_5 Tainted: G U 3.18.0-07661-g0550ce9 #1 >> [ 43.880176] Hardware name: Google Tegra210 Smaug Rev 1+ (DT) >> [ 43.885834] Call trace: >> [ 43.888294] [] dump_backtrace+0x0/0x10c >> [ 43.893697] [] show_stack+0x10/0x1c >> [ 43.898756] [] dump_stack+0x74/0xb8 >> [ 43.903814] [] warn_slowpath_common+0x84/0xb0 >> [ 43.909736] [] warn_slowpath_null+0x14/0x20 >> [ 43.915482] [] android_fence_release+0x84/0x104 >> [ 43.921582] [] fence_release+0x104/0x134 >> [ 43.927066] [] sync_fence_free+0x74/0x9c >> [ 43.932552] [] sync_fence_release+0x34/0x48 >> [ 43.938304] [] __fput+0x100/0x1b8 >> [ 43.943185] [] ____fput+0x8/0x14 >> [ 43.947982] [] task_work_run+0xb0/0xe4 >> [ 43.953297] [] do_notify_resume+0x44/0x5c >> [ 43.958867] ---[ end trace 5a2aa4027cc5d171 ]--- >> >> Let's fix it by introducing a new optional callback (disable_signaling) >> to fence operations so that drivers can do proper clean ups when we >> remove last callback for given fence. >> >> Reviewed-by: Andrew Bresticker >> Signed-off-by: Dmitry Torokhov >> > NACK! There's no way to do this race free. Can you please explain the race because as far as I can see there is not one. > The driver should hold a refcount until fence is signaled. If we are no longer interested in fence why do we need to wait for the fence to be signaled? Thanks. -- Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/